from Hacker News

Lidar-based GIS map of New Hampshire stone walls

by rob on 8/4/25, 2:40 PM with 24 comments

• by mikeocool on 8/4/25, 7:30 PM

  For folks not from New England: it's very normal to walk through inhabited the woods in New England and come upon a seemingly totally random stone wall in the middle of nowhere.

  Much of New England is 2nd(?) growth forest -- the original forests were chopped down to make space for farmland. The soil is incredibly rocky, and so farmers would go through there fields and chuck the rocks to the side, making the walls. Eventually people realized that New England's rocky soil was not very good for farming/local farming became less important as food was able to be transported longer distances, and much of the farm land was abandoned and eventually reforested -- with the only the rock walls remaining (or at least that's what I was taught growing up there).

• by PyWoody on 8/4/25, 8:10 PM

  Tom Wessels has a great chapter in Part 1 of his "Reading the Forested Landscape" video series about New England stonewalls. [0] A common myth is the walls were built over time due to the rocks being pushed up by the frost but that's not true!

  The over 125k miles of stonewalls were built in just thirty years because of sheep.

  [0] https://www.youtube.com/watch?v=zcLQz-oR6sw&t=129s

• by rob on 8/4/25, 8:51 PM

  If anybody is in Connecticut like me, here's a LiDAR map you can use for the state to find your own stone walls here:

  https://experience.arcgis.com/experience/4c801e35f200493ebff...

  ("Hillshade 2023" and "Hillshade 2023 SE illumination" are the two I use.)

• by flipnotyk on 8/4/25, 5:59 PM

  I used to work for a company that did GIS mapping of guard rails, lines, and road signs. Part of what we always ended up doing was massaging the data we received from the Lidar mapping to line things up to exact locations for clients. If this map is accurate, I salute whoever spent the time fixing the details.

• by uptime on 8/4/25, 6:53 PM

  I can see portions of a few walls that are out in spots that used to have a road over 100 years ago but now are reclaimed by the forest. Some of areas are densely overgrown now. Nice work.

• by lemonberry on 8/4/25, 4:10 PM

  This is neat. I see a few incorrect street names where I live, but also some old stone walls near where I frequently walk.

• by joshuamcginnis on 8/4/25, 7:57 PM

  This is neat. I'm curious to know what the practical uses of this information are? Anyone know?

• by jppope on 8/4/25, 6:43 PM

  very cool project and map. I've recently picked up stone masonry so this is super great to view